JPS61279793A - Shaft cooling system blower - Google Patents

Abstract

PURPOSE:To improve the volume efficiency of a dry Roots blower through reducing its temperature by providing a cooling-water circulating hole in the shaft center of the rotating shaft of the dry Roots blower so as to supply cooling water to the inside of a rotor. CONSTITUTION:In the main rotating shaft 13 and the subsidiary rotating shaft 14 of a dry Roots blower cooling-water circulating holes 13a, 14a are provided respectively. One end of each of these cooling-water circulating holes 13a, 14a is connected the cavity within an impeller, that is, a rotor 12, and the other end to a cooling-water supply chamber and a cooling-water discharge chamber on both sides. The cooling water supplied through a cooling-water supply hole 20 to the cooling-water supply chamber goes through each of these cooling-water circulating holes 13a, 14a to the cavity within the rotor 12, and hereupon, the cooling water, which becomes warm and light in specific gravity, is concentrated by a centrifugal force and then discharged through each of these cooling-water circulating holes 13a, 14a, a cooling mater discharge chamber and a cooling- water exhaust port 21 to the outside.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a dry roots blower that is of a single stage type and can provide a high pressure ratio.

[Conventional technology and problems]

When using a dry roots blower for vacuum or pressure boosting, if the pressure ratio between the suction side and the discharge side is increased in the single stage type shown in Fig. 3, the gap a between the blower casing 1 and the impeller 3, the side cover 2 Since the amount of leakage from the gap C between the impeller 3 and the impeller 3 increases, the circulation of compression heat increases, causing a temperature rise, and the impeller 3
A difference occurs between the amount of thermal expansion of the casing 92 and the amount of thermal expansion of the casing 92 exposed to the outside air, and the gap decreases, leading to burnout.

[Therefore, the achievable pressure ratio' in a single stage type is 1
・The limit is 7-2. In addition,
The pressure ratio γ is expressed by the following equation.
iPd ab
s Ps abs Ps abs: Suction side pressure
-Pd abs: When the pressure ratio is set to 1.7 to 2 or more depending on the discharge side pressure,
Conventionally, the following method has been used.
.

(・) Make B-Wa a multi-tiered type.
F'(b) Enlarge the gap of the blower. I゛・1 (C) Use backflow cooling method.
l□(d) 7'. 9-kao631□
,picture,. i) Therefore, as shown in FIG.
“・80Total pressure ratio Ra!Pa1′・°′・°(,;γ3×
・・・・・・・・・(γ1, γ2, γko: each membrane pressure ratio) j::・While a high pressure ratio can be obtained, the installation area of the blower is large and it is a single-stage type. It is also very disadvantageous in terms of price.

In the method (b), it is very difficult to set the gaps a, b, and c.

That is, as is well known, the blower discharge temperature is calculated using the following theoretical formula.

Ts ηV m Td: Discharge temperature (°K) TS: Suction temperature (6K) ηV Ni blower volumetric efficiency m: Adiabatic specific heat ratio γC: Pressure ratio - As is clear from this theoretical formula, the discharge temperature Td is the blower volumetric efficiency η9 Since the change in the gap depends on the blower
This changes the volumetric efficiency η9 and is accompanied by a change in the discharge temperature RTd.

If there is a change in the discharge temperature Td, the gap must also be changed, and as a result, it is impossible to determine the exact appropriate gap by calculation using the above theoretical formula.

Moreover, the blower efficiency η8 is η,=η,×η9(η,:
Since the blower volumetric efficiency η7 deteriorates when the gap is increased, the blower efficiency η8 deteriorates, and the shaft power becomes larger than that of the multi-stage type.

When the pressure ratio is close to 3, the shaft power of the multi-stage type is nearly double, which is problematic from an energy saving standpoint.

As shown in the principle explanatory diagrams of FIGS. 5(A) to 5(D), the method (C) described above is based on the state B ( A) Part V contains gas in a vacuum state, and low-temperature gas with the same pressure as the discharge pressure begins to flow back into part V. (B) - The backflow low-temperature gas has sufficiently flowed into part V, and the pressure in part V The state (C) in which the pressure in the part (C) approaches the discharge pressure is the same as the discharge pressure, and the operation mode is in the state (D) immediately before the discharge port and the part V communicate with each other, so the single-stage type has a certain high pressure. Although a high ratio can be obtained, the cooling effect is not sufficient because cold outside air is sucked in during the compression process, and there is a limit to the pressure ratio.

Furthermore, since the cold outside air intake port leaks before compression, it is necessary to install a cold outside air intake silencer 4 as shown in FIG. 6, which poses problems in terms of installation space and cost.

Furthermore, since cold outside air is sucked in during the compression process, it cannot be used in closed circuits with the atmosphere (for example, for hazardous gases such as toxic gases and explosive gases); In this case, as shown in FIG. 6, it is necessary to interpose an intercooler 5 on a part of the discharge side, which is disadvantageous in terms of installation area and cost.

Furthermore, since a portion of the air is returned from the discharge side, this also relates to a reduction in the blower volumetric efficiency.

More importantly, in the case of this method, the impeller 3 must have a three-blade shape, and it cannot be used with two-blade blowers manufactured with conventional equipment. There is.

'Method (d) above has a good cooling effect and gas sealing effect, and can be used up to a high pressure ratio in a single stage, but on the other hand, it cannot be used in the manufacturing process of products that dislike moisture.
(It has the disadvantage that it cannot be done.
1 [Means for solving problems]
1 This invention is the 888 method. Defects and a7. picture,. 7. [The means is that a cooling water circulation hole is provided in the axis of the rotating shaft to which the impeller is attached in a dry roots blower, and cooling water is supplied to the inside of the impeller.

Therefore, a difference in specific gravity occurs between the cooling water supplied from the rotating shaft to the inside of the impeller and the warm water that comes into contact with the inner periphery of the impeller, and due to the centrifugal force of the rotation of the inlar:
1. Warm water with light specific gravity gathers in the center of the impeller,
:i:,; Exhausted from the circulation hole of the rotating shaft and inside the impeller.
, : It has both a cooling effect on the body and a cooling effect on the exhaled gas.

be.
i ([1 [Example] Katsuyo.□, 1□□05.1o,. ,゛,' The vertical cross-sectional view in Fig. 1 and the nn cross-sectional view in Fig. 1 are
11,)1 In FIG. 2 shown, 10 is a blower casing,
・3'11 is the side cover, 12 is the two-blade impeller, ,,)13 is one impeller 1
2 is attached to the main rotation shaft, 14 is the sub-rotation shaft to which the other impeller 12 is attached, 15 is a bearing, 16 is a mechanical seal for the main rotation shaft 13 and the sub-rotation shaft 14, 17 is a pressure gauge 1
．． Reference numeral 18 indicates a suction port, and reference numeral 19 indicates a discharge port, and this configuration is the same as that of a normal dry roots blower.

The present invention provides cooling water circulation holes 13a and 14a in each axis of the main rotation shaft 13 and the sub rotation shaft 14, and provides cooling water supply holes 20 and discharge holes 21 in both side covers 11. It is characterized by

Therefore, the cooling water sent through the supply hole 20 enters the chamber 22 and flows through the cooling water distribution holes 13 of the main rotating shaft 13 and the sub rotating shaft 14.
a, 14a, enters each impeller 12, exits into the chamber 23, and is then discharged from the discharge hole 21.

That is, the cooling water cools each impeller 12 and is discharged, but at this time, a difference in specific gravity occurs between the warm water that comes into contact with the inner circumference of the impeller 12 and the cold water, and when the impeller 12 rotates, Warm water with a light specific gravity gathers in the center of the impeller 12 due to the centrifugal force of the water, and this water is discharged. Therefore, a small amount of cooling water can enhance the cooling effect of the impeller 12, and can also be used to cool the discharged gas. Function.

〔effect〕

Since the present invention supplies cooling water directly to the inside of the impeller, (a) Cold water due to the difference in specific gravity comes into contact with the inner circumference of the impeller due to the centrifugal force effect when the impeller rotates, increasing the cooling efficiency of the impeller. Furthermore, the temperature of the discharged gas is lowered, the blower efficiency is improved, and a high pressure ratio can be obtained with a single stage type.

('b) Experimental data is shown in the following table.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view showing an embodiment of the present invention, FIG. 21 is a cross-sectional view taken along line nn in FIG. An explanatory diagram of
FIGS. 5(A) to 5(D) are diagrams explaining the principle of a roots blower of the reverse flow cooling type, and FIG. 6 is a diagram explaining the flow of the roots blower of the reverse flow cooling type. 12... Impeller, 13... Main rotating shaft, 13a...
- Cooling water supply hole, 14... Sub rotating shaft, 14a... Cooling water distribution hole, 20... Cooling water supply hole, 21... Cooling water outlet. Patent applicant: Taiko Kikai Kogyo Co., Ltd. γ1 γ2 γ3 :1' □ U Skin pain □

Claims (1)

[Claims] A shaft cooling type blower characterized in that a cooling water circulation hole is provided in the axis of a rotating shaft to which an impeller is attached in a dry roots blower, and cooling water is supplied to the inside of the impeller.